Many of the electronic articles on the market today utilize various devices for alerting the user of the article to a variety of conditions. In battery-operated selective call receivers, for example, the user is alerted to the receipt of a paging message by any of a number of sensory alerting devices. One such device is an aural alert resulting from activation of a transducer such as a piezoelectric transducer. During activation of the transducer, the inductor in the transducer driver circuit may saturate and the current drain of the driver circuit may become excessive with a resultant degradation in the battery life.
The driver circuit for a transducer normally includes an inductor coil or a transformer. In small electronic articles inductors and transformers are undesirable because they are large, costly and unreliable. In addition to alert devices, inductors or transformers are necessary for certain information display devices such as electroluminescent lamps used for backlighting liquid crystal displays. Some selective call receivers include both a transducer alert device and an electroluminescent panel backlight thereby requiring two inductors or an inductor and a transformer.
Thus, what is needed is a driver circuit for a transducer and an electroluminescent lamp which includes fewer than two transformers or inductors and contains circuitry to prevent inductor saturation.